Can anyone tell me if they have done this modification, if they like it and how difficult it is for someone to do? Some people have talked about changing belts, but the kit that I was looking at changed out the chain.

I changed to 30tooth on a 07.On that year you change to what's called the international belt If I had gone only one tooth change the stock belt would have worked.It made it easier to get in 6th gear a little sooner for highway riding. Look on Andrews Cam website or S&S they have info that's very useful also Bakers.they will list years and gears and the amount each tooth drop and how it will affect your ride